12-07 Exercise 2: Function num_digits

Question

Write a function num_digits(n) that returns the number of digits in n ( a positive integer). Hint: to determine the number of digits in a number n, divide it by 10 repeatedly. when n reaches 0, the number of divisions indicates how many digits n originally had.

寫一個num_digits(n)函數 計算n有幾位數

#include <stdio.h>
int num_digits(int n)
{
   /*INSERT YOUR CODE HERE*/

   /*在這裡寫你的程式*/
   /*END OF YOUR CODE*/
}

int main(void)
{
   int n;
   scanf("%d", &n);
   printf("%d has %d digit(s)",n,num_digits(n));
   return 0;
}

Please complete this program by only insert your code between those tags:

   /*INSERT YOUR CODE HERE*/ 
   /*END OF YOUR CODE*/

Example input

12347

Example output

12347 has 5 digit(s)

Remember: You may correct the cases, but your code always be revised!

Answer 1

Hidden content!
#include <stdio.h>
int num_digits(int n)
{
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**  * * ****     ** * *  **  * *   **   ***  /= 10;
  * ***   * * * ** **  **** 
  * *   *  ****  *********  count;
}

int main(void)
{
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  * **  * ** * ******** ********  has %d * **      * *  * *  *
* **     * *  *   *** *  *  *    0;
}

Comments

Case 0: Correct output
Case 1: Correct output
Case 2: Correct output
Case 3: Correct output

Answer 2

Hidden content!
#include <stdio.h>
int num_digits(int n)
{
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}

int main(void)
{
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* **   ** **    * *    *  *  * * 0;
}

Comments

Case 0: Correct output
Case 1: Correct output
Case 2: Correct output
Case 3: Correct output

Answer 3

Hidden content!
#include ** *     ** * 
#include *** * *  **  
int num_digits(int n)
{
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}



int main(void)
{
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*       * * *   * ** **  * *   * has %d *   **  *****    *    ** 
*  *   **  ** * ** ** ***    0;
}

Comments

prog.c: In function 'num_digits':
prog.c:8:6: warning: implicit declaration of function 'abs' [-Wimplicit-function-declaration]
    n=abs(n);
      ^~~

Answer 4

Hidden content!
#include  * * *** *** *
#include *   **  * * *     
int is_prime(int n)
{
* *** *       *  * **    divisor;
if (n<=1)
    * * ** *   false;
for (divisor  **   ***       ** *** * *
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return true;
}
int main(void)
{
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  *   ** **  * *** *  * (is_prime(n)) *  *  **  ***  **  * * ** ******        ***  *   **  * *  function return 1
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   *  *   *  * *    ****      *        **** ** * ** ***  * *  ** * *
**** ***  ** ****   * ** 0;
}

Comments

Case 0: Wrong output
Case 1: Wrong output
Case 2: Wrong output
Case 3: Wrong output

Answer 5

Hidden content!
#include     *  ****** 
int num_digits(int n)
{
  **  **** ** ** *  *  *    * ** 
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* *** * * ** *** ** *  
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}

int main(void)
{
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***  * * *  **  *  ***** * ** has %d *    * ** ** ** * **  
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}

Comments

prog.c: In function 'num_digits':
prog.c:7:6: warning: implicit declaration of function 'abs' [-Wimplicit-function-declaration]
    n=abs(n);
      ^~~
prog.c:8:16: warning: implicit declaration of function 'log10' [-Wimplicit-function-declaration]
    return (int)log10(n)+1;
                ^~~~~
prog.c:8:16: warning: incompatible implicit declaration of built-in function 'log10'
prog.c:8:16: note: include '<math.h>' or provide a declaration of 'log10'

Answer 6

Hidden content!
#include <stdio.h>
int num_digits(int n)
{
***        * * * ***  ***** *** count=0;
   *  **    *  * **      ** *   * * != 0)
  ** ** *** ** * ****
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}

int main(void)
{
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****  *  * ** ***   * ***** * ****** ***  *  *  &n);
**  ***** **** ***   ** ***   * ** *  has %d  * ****  **  ****  ** ** 
 ***  * *** *** ** * ***** ** ** 0;
}

Comments

Case 0: Correct output
Case 1: Correct output
Case 2: Correct output
Case 3: Correct output

Answer 7

Hidden content!
#include <stdio.h>
int num_digits(int n)
{
***   *****   ** **** ****   cnt=0;
**  *  ***           *    *   * != 0)
*  ***   *  ** *  *****    *  *
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* ****  ** **   *  ** ** 

int main(void)
{
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    * *  *  *  *** * * **  * *  0;
}

Comments

Case 0: Correct output
Case 1: Correct output
Case 2: Correct output
Case 3: Correct output

Answer 8

Hidden content!
#include <stdio.h>
int num_digits(int n)
{
* **** ***   * *  * * *   ***  *** count=0;
*   * **   ****   * ***  **
*     ** ** *  * ** * *   * *  * != 0)
*    * ** * **    ** ** * *     
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}
int main(void)
{
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 * *   ******* ** * **       *** *  *  **  * * has %d    ** **  *****   *     **
*** ***  *  *** * *** ** * *    0;
}

Comments

Case 0: Correct output
Case 1: Correct output
Case 2: Correct output
Case 3: Correct output

Answer 9

Hidden content!
int num_digits(int n)
{
**   *   * *    *     * num_digit=0;/*INSERT YOUR CODE HERE*/
* **  *****  * * *  ****    * 
 * ***** **  **   *** 
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    *   ***   ** ** *       *    ****** **      ** **  
***    *** ** * *   **  

*  ** ** ** * **    * *  ******** *  *
  *** *   * *  *** * **  OF YOUR CODE*/
*  **** *   * ** *** **** num_digit;
}

int main(void)
{
  ** ** *  **  *   ** * n;
* ** ***    *    ** *******   *  ** ****   &n);
***** *   ***** * * *   **    *** has %d  *** **    ***  * * *** *
*** **  **** * ****  * **    0;
}

Comments

prog.c: In function 'main':
prog.c:18:4: warning: implicit declaration of function 'scanf' [-Wimplicit-function-declaration]
    scanf("%d", &n);
    ^~~~~
prog.c:18:4: warning: incompatible implicit declaration of built-in function 'scanf'
prog.c:18:4: note: include '<stdio.h>' or provide a declaration of 'scanf'
prog.c:19:4: warning: implicit declaration of function 'printf' [-Wimplicit-function-declaration]
    printf("%d has %d digit(s)",n,num_digits(n));
    ^~~~~~
prog.c:19:4: warning: incompatible implicit declaration of built-in function 'printf'
prog.c:19:4: note: include '<stdio.h>' or provide a declaration of 'printf'

Answer 10

Hidden content!
int num_digits(int n)
{
*****  ***  *        **  count=0;/*INSERT YOUR CODE HERE*/
    * ****  *   *      ** * ** 
  **  * *** * * *****   
   *** * *  * *  *** *   *   * * * * *  *   ** * **
***** *  **  *    *** *** **   **   * *  *    ***     *
  * * ** *  * *   

  *  *    *    *   *  * **    *   *   
***** *   ***   *    * OF YOUR CODE*/
 **   ** * ** * * ******  *   count;
}

int main(void)
{
**** * *   **   *   *** n;
 * *  * **** **     *   **   *  ***    &n);
 * ** * **  **  * *** ** *  **   *    has %d *  *** *  ***** **  
****   ** *    **    *  0;
}

Comments

prog.c: In function 'main':
prog.c:18:4: warning: implicit declaration of function 'scanf' [-Wimplicit-function-declaration]
    scanf("%d", &n);
    ^~~~~
prog.c:18:4: warning: incompatible implicit declaration of built-in function 'scanf'
prog.c:18:4: note: include '<stdio.h>' or provide a declaration of 'scanf'
prog.c:19:4: warning: implicit declaration of function 'printf' [-Wimplicit-function-declaration]
    printf("%d has %d digit(s)",n,num_digits(n));
    ^~~~~~
prog.c:19:4: warning: incompatible implicit declaration of built-in function 'printf'
prog.c:19:4: note: include '<stdio.h>' or provide a declaration of 'printf'